The structure of developing muscle insertions in insects.

Abstract

AbstractThe relationship between muscles and the components of the integument in muscle insertions have been studied with the electron microscope in two insects, Calpodes ethlius (Hesperiidae, Lepidoptera) and Rhodnius prolixus (Reduviidae, Hemiptera). The area of contact between the muscles and the epidermis is increased by interdigitating processes whose membranes are joined by intermediate junctions. The junctions occur at the level of a Z line so that actin filaments attach directly to them. Within the epidermis, microtubules extend from the junctions of the myoepidermal connection to the cuticle, where they attach to hemidesmosomes which line deep indentations of the membrane. The microtubules probably enable the tendinous epidermal cells to withstand the tensions exerted upon them by the muscles. The epidermis is anchored to the cuticle by tonofibrillae, homogeneous rods secreted in the deep indentations of the plasma membrane. Since the tonofibrillae of successive instars are continous, they penetrate and attach to the cuticulin, the outermost layer of the epicuticle.